1. Field of the Invention
The present invention provides an apparatus and method for injecting fluid into a balloon catheter and a device for controlling the rate and pressure of fluid injection. Such catheters, when inflated by the injected fluid, are conventionally used for the purpose of percutaneous transluminal angioplasty.
2. Description of the Prior Art
Angioplasty is a procedure for dilating arteries which are occluded or blocked. The dialation procedure is especially useful for cases of coronary artery obstructions. A special catheter is used which carries a balloon at the distal end. To re-shape an occluded artery, the balloon is inflated, for instance, by being filled and pressurized with a radiopaque fluid.
An early practitioner of the angioplasty procedure was Dr. Andreas Gruntzig of the University of Zurich. The procedure developed by Dr. Gruntzig uses a special double lumen catheter. The first lumen allows passage of a guide wire. The second lumen connects to the balloon at the distal end of the catheter, which is generally filled and pressurized with diluted contrast media. Briefly, the procedure involves inserting a guide wire into a blood vessel to be dilated and advancing the guide wire to and past the block. Next, a balloon catheter is inserted along the guide wire and advanced to the most distal portion of the block or occlusion. Then, the balloon is inflated to reform the blockage material against the artery wall. The dilated balloon creates a smooth increased-diameter inner lumen in the artery. After dilation, the balloon is collapsed and retracted. The site of the former obstruction is examined, and, if necessary, the procedure is repeated until the entire segment of the artery is dilated.
The purpose of an angioplasty inflation device is to make the balloon inflation task easier and safer. One conventional procedure is to use a syringe to expand the balloon with radiopaque dye, while watching the balloon on an x-ray monitor. An operator proceeds by judging the relative balloon size, without knowing the balloon pressure; however, the balloon may rupture if its bursting pressure is exceeded.
A well-known approach to measuring the pressure of fluid inflating the balloon is to interpose a T-fitting between the delivery end of the syringe and the balloon. In this approach, a tire pressure-type gauge or other pressure indicator is connected to the T-fitting and measures the pressure exerted by the fluid.
Typically, the angioplasty procedure is performed under relatively low level illumination to facilitate viewing the radiopaque contrast fluid on the x-ray monitor. Unfortunately, this results in difficulty in reading the pressure indicators. Additionally, since the inflated balloon entirely blocks the artery to the passage of blood, time is a critical factor in the procedure. Further, the operating physician generates and controls the inflation force on the syringe, so physician fatigue is a negative factor in the procedure.
A representative example of the prior art is provided by U.S. Pat. No. 4,439,185 to Lundquist which discloses an inflation and deflation device adapted to be used by a human hand.
The device of Lundquist includes a stop cock and an optional regulator. The preferred syringe of Lundquist has a capacity of approximately 10 cc. Lundquist teaches the use of the stop cock to maintain a predetermined pressure, thereby freeing the surgeons hands from applying pressure. A single hand may create the force that moves the piston in the syringe body, however, a second hand must be used to turn the stop cock. In an alternative embodiment, Lundquist discloses a nut threaded into a fitting and a knob mounted on a head. Pressure may be applied by turning the head. A dial-type pressure gauge is threaded onto a nipple connected to the regulator.
All of the Lundquist embodiments include a "T" shaped handle large enough so that all the fingers of the hand can grasp the handle. In addition, the portion which is adapted to be engaged by the palm is rounded to fit the palm of the hand.
U.S. Pat. No. 4,332, 254 to Lundquist teaches a system for filling and inflating and deflating a balloon-type dilating catheter used in performing coronary angioplasty procedures. The device includes a primary and secondary fluid pump assembly. Lundquist also discloses replacing a mechanical dial pressure gauge with a remote electronic pressure readout arrangement.
U.S. Pat. No. 4,244,366 to Raines discloses a syringe stroke controlling mechanism including a gripping member encircling a syringe barrel and a cap on the plunger of the syringe. In an alternative embodiment, a fastener or nut is disclosed to permit rapid stroke adjustment while retaining fine adjustment features. The nut is moved out of engagement to execute the gross adjustment, and snapped back on a threaded rod so that the threads engage the threads of the metering rod. Fine adjustments of the plunger position are made by turning the nut with the threads engaged.
U.S. Pat. No. 4,655,749 to Fischione discloses an angioplasty pressure controller including a drive screw which is connected to a piston in a cylinder and arranged for fine adjustment by turning the drive screw. An engagement slide provides a rapid means to create pressure or vacuum.
U.S. Pat. No. 4,370,982 Reilly discloses an apparatus for injecting and controlling the pressure of fluid being injected into a catheter. The apparatus provides a pressure measuring system that includes a housing for releasably and slidably holding the barrel of the syringe used to deliver fluid into the balloon catheter; and a device for measuring and indicating fluid pressure in the syringe barrel, which is also the balloon pressure. The Reilly pressure measuring system indirectly measures pressure changes of fluid in the syringe barrel by sensing movement of the barrel as a result of fluid pressure changes.
Reilly also discloses a trigger engagement of the thread sliding barrel. An engager button has a plurality of shaped members designed to fit the grooves or between lands on the threaded portion of a bolt. The button includes a recessed portion that is engaged by a pin to interconnect the button and the housing. The button is pivotable about a pin to move the raised portion into and out of engagement with the grooves on the bolt.
U.S. Pat. No. 4,429,724 to Dorros et al. discloses a pressure generator for intravascular dilators including a ram and a syringe holder. A screw drive having a large mechanical advantage is coupled for advancing the ram at a controlled rate. A coupler at one end of the ram is adapted to engage one end of the syringe plunger. The pressure generator may be provided with a pistol grip and the ram may be calibrated for direct pressure readout.